1. Field of the Invention
The present invention relates to a control system for a magnetic disk drive system and, more particularly, to circuitry for use with a servo system to control movement of a read/write transducer associated with a magnetic disk drive system.
2. Description of the Prior Art
In the field of electronic data handling, it is conventional to store data in binary form on the face of a rotatable disk. In operation, such a disk is rotated by a so-called spindle motor and the binary data is encoded upon, or retrieved from, the face of the disk by a movable electromagnetic transducer device often referred to as a read/write head. More particularly, the binary information is magnetically encoded on the face of the disk in concentric rings, called tracks, and the read/write transducer is selectively positioned by a pivoted read/write arm to move across the face of the disk in order to locate a particular track at which information is to be recorded or retrieved. Once a desired track is located, rotation of the magnetic disk will bring the read/write transducer to a particular location on the track, called a sector location, at which the read or write operation will be accomplished. A typical five and one-quarter inch diameter disk, for example, has four hundred to six hundred tracks for data storage and thirty-two sectors per track.
In many magnetic recording disk systems, the read/write transducer is driven to seek a desired track on the disk by means of a motor and an associated mechanism which translate electrical commands from a controller for the disk drive system to discrete steps of the read/write transducer arm across the face of the magnetic recording disk. In such systems, to accurately locate the read/write transducer at a particular location on a desired track on a magnetic disk, it is necessary that the controller receive orientation information. As one source of such information, it is typical to magnetically write orientation information upon the face of the magnetic disk so that, by reading such information, the read/write transducer is able to determine its location upon the disk. A drawback of such an approach, however, is that the space taken up on the face of the disk for the orientation information could be otherwise utilized for data storage. Accordingly, if orientation information is written upon the face of a magnetic disk, it is desirable to keep such information brief, i.e., to minimize the physical space needed to store such orientation information.